Low pressure exhauster



Nov. 7, 1961 A. Y. DODGE Low PRESSURE ExHAusTER Filed April 3, 1961 (lll ,l n, iA

I NV EN TOR.l

ATTO/MHS.

Wyo@ MMM United States 'Ilhis invention relates to a low pressure exhauster and more particularly to `an -apparatus for pumping large volumes of vapor for the like at low absolute pressures.

In handling vapors and the like at low absolute pressures for evaporating a liquid from a container, or similar closed space, it becomes necessary to pump extremely large volumes of very low density iiuid. Piston pumps and rotary vane pumps become too large to be practical for this purpose and centrifugal pumps are extremely ineicient due to the lo-w density of the lluid'.

It is therefore one of the objects of the present invention .to provide a low pressure exhauster which functions with a high `degree of efficiency to pump large volumes of vapor and the like at an extremely low |absolute pressure.

Another object is to provide a low pressure exhauster in which a pontion of the vapor to be pumped is Withdrawn from a container by a mechanical pump and is compressed thereby, the compressed vapor being supplied to a jet ejector connected 4to the same container to withdraw an additional and larger volume of vapor therefrom.

According to a further feature of the invention, the principles thereof may be incorporated in a closed cooling system using water or similar liquid as a cooling medium by evacuating vapor from la container under low pressure, condensing the vapor and returning the condensate to the original container. In such a system an auxiliary vacuum pump is preferably provided and is automatically controlled to maintain a predetermined degree of subatmospheric pressure in the system.

The invention is also applicable in evaporating systems either for dehydration or distillation by supplying a liquid to be evaporated to a container and collecting the condensate in a second container from which it may be removed by a pump.

Various other applications of the invention as well as other objects and advantages thereof will be more readily `apparent from the following description when read in connection with lche accompanying drawing, in which:

FIGURE 1 is an elevation with parts in section of a low pressure exhauster system embodying the invention;

and

FIGURE 2 is an enlarged partial sectional View through an alternative form ot jet ejector.

As shown in FIGURE 1, a liquid or similar material to be subjected to low pressure isV contained in -a closed container 10. The upper part of the container above the normal level of liquid therein is connected to the inlet of a mechanical pump 11 which is driven by a motor 12. The upper part of the container is also connected through a conduit 13 to a jet ejector, indicated generally at 14. As shown in FIGURE 1, the jet ejector comprises lan outer Atubular casing 15 dening an `outer passage communicating with the conduit 13 and a central nozzle 16 connected through a conduit 17 to the discharge opening of the pump 11. A reduced throat 1S is provided beyond the discharge nozzle 16 and communicates with a tapered diluser chamber 19 which is preferably provided with cooling lins 21 on its exterior and with a series of cooling tubes 22 extending thereacross and through which a cooling medium, such `as air, may be circulated by a fan 23. Cooling of the tapered diffuser chamber 19 lby the iins and Iby the cooling tubes 22 will condense vapor entering the diiuser chamber and the condensate Fmire will drain from the bottom of the diffuser chamber through 'a conduit 24 past a check valve Z5 and into a second container 26. A vacuum pump 27 is connected to the upper par-t of the second container 26 and is driven by a motor 28 controlled by a switch 29 responsive to the pressure in the container 26 to maintain a consta-nt static pressure therein. Condensate collecting in the container 26 may be withdrawn therefrom -by `a liquid pump 30. t

'I'he container 10 may be supplied with liquid to be evaporated through an inlet connection 31 controlled by a valve 32 and communicating with lany desired source of liquid. A pump 33 may be connected to the lower, part of the container 10 to remove liquid therefrom when desired.

For various uses of the exlilauster, the container 10 may form `a part of a heat exchanger which is completed by a coil 34 in the container 10 and having external connections 35. A second fluid may be circulated through the coil 34 in heat exchanging relation with the material in the container 10 for -various processes employing the exhauster.

One useful purpose lof the exhauster is to provide a secondary cooling system for use in cooling apparatus, as more particularly disclosed iand claimed in my co-pending 1application Serial No. 49,661. For this purpose, water can be used as the cooling medium and the container 10 will be lilled with water to a level below the connection to the pump 11. In this case, the outlet port of the pump 30 will be connected through the valve 32 to the supply port 31 of the container 10 to recirculate the condensate in a cooling cycle. Preferably for cooling, the static pressure in the system is reduced by the vacuum pump 27 .to approximately 2.5 p.s.i.a. When the pump 11 is operating, it will reduce the pressure in the upper part of the container 10 to about .5 p.s.i.a. and will compress the vapor so withdrawn to about l() p.s.i.a. The compressed vapor discharged through the nozzle 16 will induce flow of a substantially larger volume of vapor from the upper part of the container 10 at about .5 p.s.i.a. and the mixture of vapors will vdischarge into the diffuser chamber 19 at about 2.5 p.s.i.a. As the vapors are condensed, they will flow by gravity into the second container Z6 and can be returned by the pump 30 to Ithe -rst container 10 in a closed cycle. The pressure and temperature in the iirst container may be indicated by a suitable gauge 36 yand thermometer 37 and liuctuations in the compressed vapor discharged by the pump 11 may be damped out by an equalizer 38.

For this use of the exhauster, the coil 34 may serve as a condenser for `a primary refrigerant which is circulated therethrough in a closed refrigerating cycle. The Water in the container 10 will be maintained at a relatively low temperature by evaporation with the heat ultimately being `dissipated to the air from the condenser.

In one example of this use, let it be assumed that it is desired to exhaust cubic feet per minute of water vapor from the container 10 at a pressure of .5 p.s.i.a. at 80 F. Water vapor at the .5 p.s.i.a. and 80 F. weighs %33 pound per cubic foot and is at very low density. The pump 1=1 will pump about 30 cubic feet per minute of water vapor from the container 11 and will discharge compressed vapor [at l0 p.s.i.a. and about 220 F. lThis hot vapor is mixed With two to three volumes of cool vapor in the ejector and due to this mixing and to the subsequent reconversion of ow -to pressure, the vapor will discharge into the condenser at labout F. 'Ihe hot vapor will be cooled by the condenser to approximately atmospheric temperature Iand the condensate will be collected in the container 26 and returned to the iirSt container 10 Iat ya temperautre some 10 above ambient temperature. Therefore, with the .present apparatus a 3 pump having a capacity of about one-fourth of the total volume of vapor to be pumped can be employed so that the Iapparatus does notv become excessive in size and can function with a high degree of efliciency.

In using the invention for evaporating as, for example, in a distilling operation, the liquid to be distilled is supplied to the container through the valve 32 and inlet port 31 and is evaporated under the same conditions as described above in connection with cooling. In this operation, heat may be supplied to the coil 34 as, for example, by circulating hot water or steam therethrough to increase the rate of evaporation. The condensate collected in the second container 26 may be withdrawn therefrom by the pump 3f)l and taken to a desired point of use. '111e enriched liquid remaining in the container 1i! may be withdrawn therefrom by the pump 33 either periodically or continuously, depending upon the material being evaporated.

The apparatus may also be used for dehydrating or concentrating operations by placing the liquid to be dehydrated or concentrated in the container if) and proceeding in the same manner as in an evaporating operation. When the material has reached the desired degree of dehydration or concentration, it may be withdrawn from the container 19 by the pump 33. Alternatively, where the material is dehydrated `to complete dryness, the container 10 could be opened and the dried material removed therefrom in a batch process.

It will be apparent that in addition to the operations specifically described, the invention could be employed in any process wherein it is desirable to pump large volumes of vapors or Similar fluids at low pressure and the specific uses enumerated above lare intended only to be examples of those to which the invention may be applied.

FIGURE 2 illustrates an alternative form of ejector which may be used with advantage to provide somewhat improved efliciencies. In this construction, the ejector comprises an outer tapered casing 41v to provide it with a tangential inlet opening 42 adjacent to its large end and with a tapered nozzle 43 extending coaxially therewith. The nozzle is provided with a conduit connection 44 extending through the large end of the casing 41 for connection, for example, to the outlet of the pump 11. The casing 41 tapers `to la reduced throat 45 formed with a connecting flange 46 through which it may be connected to the diffuser chamber 19.

In this construction, the nozzle has a helically twisted strip 47 therein to cause the fluid owing therethrough to swirl in a counterclockwise direction viewed in the direction of low of the fluid. Similar vanes or guide strips 48 are provided in the space between the nozzle 43 and the casing 41 to cause the fluid flowing through lthis space to swirl in the same direction.

In operation of this form of nozzle, the fluid flowing through both of the passages thereof will be caused to swirl atan extremely high angular velocity thus tending to produce a low pressure core at the center of the swirling vortex. As the swirling material enters the diffuser chamber, it expands outward radially thus tending to accent the low pressure existing at the axis of the vortex and increasing the effectiveness of the ejector so that a smaller quantity of high pressure fluid will be required flowing through the nozzle (outer annular space) to eject the same quantity of fluid flowing through the inner passage.

While two embodiments or" the invention have been shown and described herein, it will be understood that they are illustrative only and not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

l. A low pressure exhauster comprising a container defining a space to be exhausted, a pump having an inlet and `an outlet, a first conduit connecting the upper part of the space to the pump inlet whereby the pump will withdraw vapor therefrom and increase the pressure on the vapor, a jet ejector including two` passages, a second conduit connecting one of the passages to the pump outlet to receive vapor under increased pressure therefrom, and a third conduit separate from the first conduit connecting the other of said passages directly to the space, discharge of the vapor under increased pressure through said one of the passages inducing flow of a larger volume of vapor from the space through the third conduit and the other of the passages.

2. A low pressure exhauster comprising `a container defining a space to be exhausted, a pump connected to the space to withdraw vapor therefrom and to increase the pressure on the vapor, a jet ejector including two passages, a conduit connecting one of the passages to the pump to -receive vapor under increased pressure therefrom, and a conduit connecting the other of said passages directly to the space, discharge of the vapor under increased pressure through said one of the passages inducing flow of a larger volume of vapor from the space through the last named conduit and the other of the passages, a condenser receiving the vapor from the jet ejector, and means for maintaining the condenser under subatmospheric pressure.

3. A low pressure exhauster comprising a container defining a space to be exhausted, a pump connected to the space to withdraw vapor therefrom and to increase the pressure on the vapor, a jet ejector including two passages, a conduit connecting one of the passages to the pump to receive vapor under increased pressure therefrom, and a conduit connecting the other of said passages directly to the space, discharge of the vapor under increased pressure through said one of the passages inducing flow of a larger volume of vapor from the space through the last named conduit and the other of the passages, a condenser receiving `the vapor from the jet ejector, a second container receiving condensate from the condenser, and means to maintain the second container and the condenser under subatmospheric pressure.

4. The low pressureexhauster of claim 3 in which the last named means comprises a pump connected to the second container to pump condensate therefrom and a vacuum pump connected to the upper part of the second container to maintain a predetermined subatmospheric pressure therein.

5. In a cooling system, a first container adapted to contain a liquid to be cooled, a pump having its inlet connected to the upper part of the container to withdraw vapor therefrom yand to compress the vapor, a jet ejector including two passages, a connection from one of said passages to the upper part of the container to receive vapor therefrom, a connection from the outlet of the pump to the other of said passages, a condenser receiving vapor discharged from the jet ejector and condensing it, a second container receiving condensate from the condenser, a connection from the second container to the first container to return condensate to the first container, the containers and connections forming a closed system, and a vacuum pump connected to said system to maintain a predetermined static pressure therein.

6. The system of claim 5 including means in the first container to circulate a fluid therethrough separate from but in heat exchanging relationship with the liquid in the first container.

7. In an evaporating system, a rst container adapted to contain a liquid to be evaporated, a pump having its inlet connected Ato the upper part of the container to withdraw vapor therefrom and to compress the vapor, a jet ejector including two passages, a connection from the upper part of the container to one of said passages for flow of vapor therethrough, a connection from the outlet of the pump to the other of said passages to supply compressed vapor thereto, a condenser receiving vapor discharged from the jet ejector and condensing it, means to supply liquid to be vaporized to the first container, and means to remove condensate from the condenser under subatmospheric pressure.

8. In an evaporating system, a first container adapted to contain a liquid to be evaporated, a. pump having its inlet connected to the upper part of the container to Withdraw vapor therefrom and to compress the vapor, a jet ejector including tWo passages, a connection from the upper part of the container to one of said passages for ow of vapor therethrough, a connection from the outlet of the pump to the other of said passages to supply compressed vapor thereto, a. condenser receiving vapor discharged from the jet ejector and condensing it, means to supply liquid to be vaporized to the first container, a second container receiving condensate from the condenser, a vacuum pump connected to the upper part of the second container to maintain la subatm'ospheric pressure therein, and a liquid pump connected to the lower part of the second container to Withdraw condensate therefrom.

9. The evaporating system of claim 7 including means in the container to circulate a uid therethrough separate from but in heat exchanging relationship with the liquid in the container.

l0. The evaporating system of claim 8 including a cont-rol for the vacuum pump responsive to the pressure in the second container.

References Cited in the le of this patent UNITED STATES PATENTS 1,082,113 Diden Dec. 23, 1913 2,095,534 Schmidt Oct. 12, 1939 2,295,462 Forman Sept. 8, 1942 2,774,230 Kasser Dec. 18, 1956 

